Method and apparatus for eliminating chromatic aberration

Abstract

A method and an apparatus for eliminating chromatic aberration are provided. The method includes: calculating out a position weight of a pixel according to the position of the pixel in an image, calculating out an edge response of the pixel and converting a chrominance of the image pixel into a hue; using the edge response of the pixel to calculate out a hue range; and finally correcting the hue of the image pixel by using the position weight, the edge response and/or the hue range.

What is claimed is: 
     
         1 . A method for eliminating chromatic aberration, comprising:
 calculating a position weight of a pixel according to position of the pixel in an image; and   correcting original chrominance of the pixel by using the position weight.   
     
     
         2 . The method for eliminating chromatic aberration as claimed in  claim 1 , wherein step of calculating the position weight of the pixel comprises:
 calculating the position weight of the pixel according to relative distance between the pixel and center coordinates of the image.   
     
     
         3 . The method for eliminating chromatic aberration as claimed in  claim 2 , wherein the operation of calculating the position weight of the pixel comprises:
 calculating the position weight W R =[(X i −X 0 ) 2 +(Y i −Y 0 ) 2 ]/[(X max −X 0 ) 2 +(Y max −Y 0 ) 2 ], wherein (X 0 , Y 0 ) are the center coordinates of the image, (X i  and Y i ) are coordinates of the pixel, X max  is maximal value among the X-axis of the image and Y max  is maximal value among the Y-axis of the image.   
     
     
         4 . The method for eliminating chromatic aberration as claimed in  claim 1 , wherein the operation of correcting original chrominance of the pixel comprises:
 defining a position weight threshold;   comparing the position weight with the position weight threshold to obtain a comparison result; and   deciding whether to correct the original chrominance of the pixel according to the comparison result.   
     
     
         5 . The method for eliminating chromatic aberration as claimed in  claim 4 , wherein the step of deciding whether to correct the original chrominance of the pixel according to the comparison result comprises:
 if the position weight is greater than the position weight threshold, correcting the original chrominance of the pixel; and   if the position weight is less than the position weight threshold, not correcting the original chrominance of the pixel.   
     
     
         6 . The method for eliminating chromatic aberration as claimed in  claim 1 , wherein the original chrominance of the pixel comprises a chroma component Cb and a chroma component Cr, and the operation of correcting the original chrominance of the pixel comprises:
 calculating a new chroma component Cb′=Cb×W R ×W NORMAL ; and   calculating a new chroma component Cr′=Cr×W R ×W NORMAL ;   wherein W R  is the position weight, and W NORMAL  is a normalized parameter.   
     
     
         7 . The method for eliminating chromatic aberration as claimed in  claim 1 , wherein the original chrominance of the pixel comprises a chroma component Cb and a chroma component Cr, and the operation of correcting the original chrominance of the pixel comprises:
 calculating a new chroma component Cb′=Cb×W NORMAL ÷W R ; and   calculating a new chroma component Cr′=Cr×W NORMAL ÷W R ;   wherein W R  is the position weight, and W NORMAL  is a normalized parameter.   
     
     
         8 . The method for eliminating chromatic aberration as claimed in  claim 1 , further comprising:
 calculating an edge response of the pixel according to a luminance of the image;   wherein the operation of correcting the original chrominance of the pixel further uses the edge response and the position weight to correct the original chrominance of the pixel.   
     
     
         9 . The method for eliminating chromatic aberration as claimed in  claim 8 , wherein the edge response is a positive detail intensity response or a negative detail intensity response, and the operation of calculating the edge response comprises:
 performing a detail intensity calculation on the luminance of the image by using a filter, so as to obtain the positive detail intensity response or the negative detail intensity response of the pixel.   
     
     
         10 . The method for eliminating chromatic aberration as claimed in  claim 8 , wherein the edge response is a positive detail intensity response or a negative detail intensity response, and the operation of correcting the original chrominance of the pixel comprises:
 defining a position weight threshold, a positive detail intensity response threshold and a negative detail intensity response threshold;   if the edge response is the positive detail intensity response, converting the positive detail intensity response into a positive detail intensity response weight;   if the edge response is the negative detail intensity response, converting the negative detail intensity response into a negative detail intensity response weight;   comparing the position weight with the position weight threshold, and comparing the positive detail intensity response with the positive detail intensity response threshold or comparing an absolute value of the negative detail intensity response with the negative detail intensity response threshold; and   deciding whether to correct the original chrominance of the pixel according to the comparison results.   
     
     
         11 . The method for eliminating chromatic aberration as claimed in  claim 10 , wherein the step of deciding whether to correct the original chrominance of the pixel according to the comparison results comprises:
 if the position weight is greater than the position weight threshold, and the positive detail intensity response is greater than the positive detail intensity response threshold, correcting the original chrominance of the pixel; and   if the position weight is greater than the position weight threshold, and the absolute value of the negative detail intensity response is greater than the negative detail intensity response threshold, correcting the original chrominance of the pixel.   
     
     
         12 . The method for eliminating chromatic aberration as claimed in  claim 11 , wherein the original chrominance of the pixel comprises a chroma component Cb and a chroma component Cr, and the operation of correcting the original chrominance of the pixel comprises:
 calculating a new chroma component Cb′=Cb×(W R +W IP )×W NORMAL ; and   calculating a new chroma component Cr′=Cr×(W R +W IP )×W NORMAL ;   wherein W R  is the position weigh, W IP  is the positive detail intensity response weight, and W NORMAL  is a normalized parameter.   
     
     
         13 . The method for eliminating chromatic aberration as claimed in  claim 11 , wherein the original chrominance of the pixel comprises a chroma component Cb and a chroma component Cr, and the operation of correcting the original chrominance of the pixel comprises:
 calculating a new chroma component Cb′=Cb×(W R +W IN )×W NORMAL ; and   calculating a new chroma component Cr′=Cr×(W R +W IN )×W NORMAL ;   wherein W R  is the position weight, W IN  is the negative detail intensity response weight, and W NORMAL  is a normalized parameter.   
     
     
         14 . The method for eliminating chromatic aberration as claimed in  claim 11 , wherein the original chrominance of the pixel comprises a chroma component Cb and a chroma component Cr, and the operation of correcting the original chrominance of the pixel comprises:
 calculating a new chroma component Cb′=Cb×W NORMAL ÷(W R +W IP ); and   calculating a new chroma component Cr′=Cr×W NORMAL ÷(W R +W IP );   wherein W R  is the position weight, W IP  is the positive detail intensity response weight, and W NORMAL  is a normalized parameter.   
     
     
         15 . The method for eliminating chromatic aberration as claimed in  claim 11 , wherein the original chrominance of the pixel comprises a chroma component Cb and a chroma component Cr, and the operation of correcting the original chrominance of the pixel comprises:
 calculating a new chroma component Cb′=Cb×W NORMAL ÷(W R +W IN ); and   calculating a new chroma component Cr′=Cr×W NORMAL ÷(W R +W IN );   wherein W R  is the position weight, W IN  is the negative detail intensity response weight, and W NORMAL  is a normalized parameter.   
     
     
         16 . The method for eliminating chromatic aberration as claimed in  claim 1 , further comprising:
 calculating an edge response of the pixel according to a luminance of the image;   converting the edge response into a hue range; and   converting the chrominance of the pixel into a hue;   wherein the operation of correcting the original chrominance of the pixel further uses the edge response, the hue, the hue range and the position weight to correct the original chrominance of the pixel.   
     
     
         17 . The method for eliminating chromatic aberration as claimed in  claim 16 , wherein the edge response is a positive detail intensity response or a negative detail intensity response, and the operation of calculating the edge response comprises:
 performing a detail intensity calculation on the luminance of the image by using a filter, so as to obtain the positive detail intensity response or the negative detail intensity response of the pixel.   
     
     
         18 . The method for eliminating chromatic aberration as claimed in  claim 16 , wherein the edge response is a positive detail intensity response or a negative detail intensity response, and the operation of correcting the original chrominance of the pixel comprises:
 defining a position weight threshold, a positive detail intensity response threshold and a negative detail intensity response threshold;   if the edge response is the positive detail intensity response, converting the positive detail intensity response into a positive detail intensity response weight;   if the edge response is the negative detail intensity response, converting the negative detail intensity response into a negative detail intensity response weight;   comparing the position weight with the position weight threshold, comparing the positive detail intensity response with the positive detail intensity response threshold or comparing an absolute value of the negative detail intensity response with the negative detail intensity response threshold, and comparing the hue with the hue range; and   deciding whether to correct the original chrominance of the pixel according to the comparison results.   
     
     
         19 . The method for eliminating chromatic aberration as claimed in  claim 18 , wherein the step of deciding whether to correct the original chrominance of the pixel according to the comparison results comprises:
 correcting the original chrominance of the pixel by using a first normalized parameter, the positive detail intensity response weight and the position weight if the position weight is greater than the position weight threshold, the positive detail intensity response is greater than the positive detail intensity response threshold and the hue is within the hue range; and   correcting the original chrominance of the pixel by using the first normalized parameter, the negative detail intensity response weight and the position weight if the position weight is greater than the position weight threshold, the absolute value of the negative detail intensity response is greater than the negative detail intensity response threshold and the hue is within the hue range.   
     
     
         20 . The method for eliminating chromatic aberration as claimed in  claim 19 , wherein the step of deciding whether to correct the original chrominance of the pixel according to the comparison results comprises:
 correcting the original chrominance of the pixel by using a second normalized parameter, the positive detail intensity response weight and the position weight if the position weight is greater than the position weight threshold, the positive detail intensity response is greater than the positive detail intensity response threshold and the hue is not within the hue range; and   correcting the original chrominance of the pixel by using the second normalized parameter, the negative detail intensity response weight and the position weight if the position weight is greater than the position weight threshold, the absolute value of the negative detail intensity response is greater than the negative detail intensity response threshold and the hue is not within the hue range.   
     
     
         21 . The method for eliminating chromatic aberration as claimed in  claim 19 , wherein the original chrominance of the pixel comprises a chroma component Cb and a chroma component Cr, and the operation of correcting the original chrominance of the pixel comprises:
 calculating a new chroma component Cb′=Cb×W NORMAL1 ÷(W R +W IP ); and   calculating a new chroma component Cr′=Cr×W NORMAL1 ÷(W R +W IP );   wherein W R  is the position weigh, W IP  is the positive detail intensity response weight and W NORMAL1  is the first normalized parameter.   
     
     
         22 . The method for eliminating chromatic aberration as claimed in  claim 19 , wherein the original chrominance of the pixel comprises a chroma component Cb and a chroma component Cr, and the operation of correcting the original chrominance of the pixel comprises:
 calculating a new chroma component Cb′=Cb×W NORMAL1 ÷(W R +W IN ); and   calculating a new chroma component Cr′=Cr×W NORMAL1 ÷(W R +W IN );   wherein W R  is the position weight, W IN  is the negative detail intensity response weight and W NORMAL1  is the first normalized parameter.   
     
     
         23 . The method for eliminating chromatic aberration as claimed in  claim 20 , wherein the original chrominance of the pixel comprises a chroma component Cb and a chroma component Cr, and the operation of correcting the original chrominance of the pixel comprises:
 calculating a new chroma component Cb′=Cb×W NORMAL2 ÷(W R +W IP ); and   calculating a new chroma component Cr′=Cr×W NORMAL2 ÷(W R +W IP );   wherein W R  is the position weigh, W IP  is the positive detail intensity response weight and W NORMAL2  is the second normalized parameter.   
     
     
         24 . The method for eliminating chromatic aberration as claimed in  claim 20 , wherein the original chrominance of the pixel comprises a chroma component Cb and a chroma component Cr, and the operation of correcting the original chrominance of the pixel comprises:
 calculating a new chroma component Cb′=Cb×W NORMAL2 ÷(W R +W IN ); and   calculating a new chroma component Cr′=Cr×W NORMAL2 ÷(W R +W IN );   wherein W R  is the position weight, W IN  is the negative detail intensity response weight and W NORMAL2  is the second normalized parameter.   
     
     
         25 . An apparatus for eliminating chromatic aberration, comprising:
 a position weight calculation unit, receiving data of the pixel and calculating a position weight of the pixel according to position of the pixel in an image; and   a chrominance correction unit, coupled to the position weight calculation unit, wherein the chrominance correction unit corrects original chrominance of the pixel by using the position weight.   
     
     
         26 . The apparatus for eliminating chromatic aberration as claimed in  claim 25 , wherein the position weight calculation unit calculates the position weight of the pixel according to relative distance between the pixel and center coordinates of the image. 
     
     
         27 . The apparatus for eliminating chromatic aberration as claimed in  claim 26 , wherein the position weight calculation unit calculates the position weight W R =[(X i −X 0 ) 2 +(Y i −Y 0 ) 2 ]/[X max −X 0 ) 2 +(Y max −Y 0 ) 2 ], wherein (X 0 , Y 0 ) are the center coordinates of the image, (X i  and Y i ) are coordinates of the pixel, X max  is maximal value among the X-axis of the image and Y max  is maximal value among the Y-axis of the image. 
     
     
         28 . The apparatus for eliminating chromatic aberration as claimed in  claim 25 , wherein the chrominance correction unit compares the position weight with a position weight threshold and decides whether to correct the original chrominance of the pixel according to the comparison result. 
     
     
         29 . The apparatus for eliminating chromatic aberration as claimed in  claim 25 , further comprising:
 an edge response unit, coupled to the chrominance correction unit, wherein the edge response unit receives the data of the pixel and calculates an edge response of the pixel according to a luminance of the image,   wherein the chrominance correction unit further uses the edge response and the position weight to correct the original chrominance of the pixel.   
     
     
         30 . The apparatus for eliminating chromatic aberration as claimed in  claim 29 , wherein the edge response is a positive detail intensity response or a negative detail intensity response, and the chrominance correction unit defines a position weight threshold, a positive detail intensity response threshold and a negative detail intensity response threshold; the chrominance correction unit converts the positive detail intensity response into a positive detail intensity response weight if the edge response is the positive detail intensity response; the chrominance correction unit converts the negative detail intensity response into a negative detail intensity response weight if the edge response is the negative detail intensity response; the chrominance correction unit compares the position weight with the position weight threshold, and compares the positive detail intensity response with the positive detail intensity response threshold or compares an absolute value of the negative detail intensity response with the negative detail intensity response threshold; and the chrominance correction unit decides whether to correct the original chrominance of the pixel according to the comparison results. 
     
     
         31 . The apparatus for eliminating chromatic aberration as claimed in  claim 30 , wherein
 the chrominance correction unit corrects the original chrominance of the pixel if the position weight is greater than the position weight threshold and the positive detail intensity response is greater than the positive detail intensity response threshold; and the chrominance correction unit corrects the original chrominance of the pixel if the position weight is greater than the position weight threshold and the absolute value of the negative detail intensity response is greater than the negative detail intensity response threshold.   
     
     
         32 . The apparatus for eliminating chromatic aberration as claimed in  claim 25 , further comprising:
 an edge response unit, coupled to the chrominance correction unit, wherein the edge response unit receives the data of the pixel and calculates an edge response according to a luminance of the image;   a chrominance converting unit, receiving the data of the pixel and converts the chrominance of the pixel into a hue; and   a hue calculation unit, coupled to the chrominance converting unit and the chrominance correction unit, wherein the hue calculation unit converts the edge response into a hue range;   wherein the chrominance correction unit further uses the edge response, the hue, the hue range and the position weight to correct the original chrominance of the pixel.   
     
     
         33 . The apparatus for eliminating chromatic aberration as claimed in  claim 32 , wherein the edge response is a positive detail intensity response or a negative detail intensity response, and the chrominance correction unit defines a position weight threshold, a positive detail intensity response threshold and a negative detail intensity response threshold; the chrominance correction unit converts the positive detail intensity response into a positive detail intensity response weight if the edge response is the positive detail intensity response; the chrominance correction unit converts the negative detail intensity response into a negative detail intensity response weight if the edge response is the negative detail intensity response; the chrominance correction unit compares the position weight with the position weight threshold, compares the positive detail intensity response with the positive detail intensity response threshold or compares an absolute value of the negative detail intensity response with the negative detail intensity response threshold, and compares the hue with the hue range; and the chrominance correction unit decides whether to correct the original chrominance of the pixel according to the comparison results. 
     
     
         34 . The apparatus for eliminating chromatic aberration as claimed in  claim 33 , wherein the chrominance correction unit corrects the original chrominance of the pixel by using a first normalized parameter, the positive detail intensity response weight and the position weight if the position weight is greater than the position weight threshold, the positive detail intensity response is greater than the positive detail intensity response threshold and the hue is within the hue range; and the chrominance correction unit corrects the original chrominance of the pixel by using the first normalized parameter, the negative detail intensity response weight and the position weight if the position weight is greater than the position weight threshold, the absolute value of the negative detail intensity response is greater than the negative detail intensity response threshold and the hue is within the hue range. 
     
     
         35 . The apparatus for eliminating chromatic aberration as claimed in  claim 33 , wherein
 the chrominance correction unit corrects the original chrominance of the pixel by using a second normalized parameter, the positive detail intensity response weight and the position weight if the position weight is greater than the position weight threshold, the positive detail intensity response is greater than the positive detail intensity response threshold and the hue is not within the hue range; and   the chrominance correction unit corrects the original chrominance of the pixel by using the second normalized parameter, the negative detail intensity response weight and the position weight if the position weight is greater than the position weight threshold, the absolute value of the negative detail intensity response is greater than the negative detail intensity response threshold and the hue is not within the hue range.   
     
     
         36 . A method for eliminating chromatic aberration, comprising:
 calculating a position weight of a pixel according to relative distance between the pixel and center coordinates of an image;   calculating an edge response of the pixel according to a luminance of the image;   converting the edge response into a hue range; and   converting the chrominance of the pixel into a hue; and   correcting original chrominance of the pixel by using the edge response, the hue, the hue range and position weight.   
     
     
         37 . The method for eliminating chromatic aberration as claimed in  claim 36 , wherein the edge response is a positive detail intensity response or a negative detail intensity response, and the operation of calculating the edge response comprises:
 performing a detail intensity calculation on the luminance of the image by using a filter, so as to obtain the positive detail intensity response or the negative detail intensity response of the pixel.